Communication device, mobile communication system, control method, and program

Abstract

A communication device operating as an IAB donor configured to communicate with a first IAB node in a mobile communication system, the communication device comprising: detection means for detecting a second IAB node different from the first IAB node; and a transmitting means for transmitting a switching request for switching the user equipment connected to the first IAB node to the second IAB node according to the detection means detecting the second IAB node.

Description

Technical Field

[0001] The present invention relates to load distribution processing of communications in a mobile communication system. Background Art

[0002] exist In the 3rd Generation Partnership Project (3rd Generation Partnership Project), IAB (Integrated Access and Backhaul) has been standardized as a communication technology for backhaul. IAB is a technology that uses access communication between a base station and UE (User Equipment) as backhaul communication at the same time (PTL1). For IAB, for example, millimeter wave radio communication in the 28 GHz band or the like is used.

[0003] In backhaul communications using IAB technology, a relay device called an IAB node relays communications from a base station called an IAB donor through millimeter wave communications. By using IAB technology, the coverage of an area can be expanded at a low cost compared to wired communications through conventional optical fibers, etc.

[0004] In addition, a technology is also proposed in which the UE monitors the radio link status and issues a failure notification to the base station if a problem occurs, and the base station receiving the notification requests the UE to perform handover as needed (PTL 2).

[0005] If IAB is used, the UE periodically notifies the base station of surrounding environment information (such as radio wave strength information between the UE and the surrounding IAB nodes) in backhaul communication. After receiving the surrounding environment information from the UE, the base station requests the user equipment to perform a handover to another IAB node as needed.

[0006] Citation List

[0007] Patent Literature

[0008] PTL1: Japanese Patent Publication No. 2019-534625

[0009] PTL2: Japanese Patent Publication No. 2018-121345 Summary of the invention

[0010] Technical issues

[0011] When many UEs are concentrated (venue events, large offline events, disaster sites, etc.), the surrounding IAB nodes connected to these many UEs may reach a high load state. In addition, if the relay station cannot operate due to a disaster, the relatively surviving relay stations may reach a high load state.

[0012] In this case, in order to reduce the load on the IAB node, an IAB node (hereinafter referred to as a "spare IAB node") may be installed, which is installed in a vehicle or the like and can be used as a temporary relay station. In that case, it is necessary to try to perform appropriate load distribution between the IAB node in a high load state and the spare IAB node.

[0013] However, in conventional handover techniques, handover is performed only when the UE is disconnected from the currently connected IAB node or when the base station recognizes that handover is necessary based on the surrounding environment information collected from the UE. In the above state, since the radio wave strength between the UE and the IAB node is not reduced, the disconnection decision is not made. In addition, due to congestion, the notification of surrounding environment information from the UE to the base station may be significantly delayed. Therefore, there is a problem that it is difficult to quickly distribute the load using the backup IAB node.

[0014] The present invention has been made in view of the above-mentioned problems, and provides a technology capable of achieving more efficient communication.

[0015] Solution to the problem

[0016] In order to solve the above problem, the communication device according to the present invention has the following arrangement. That is, a communication device operating as an IAB (Integrated Access and Backhaul) donor, the IAB donor is configured to communicate with a first IAB node in a mobile communication system, and the communication device includes:

[0017] a detection device, configured to detect a second IAB node different from the first IAB node, and

[0018] The sending means is used to send a switching request for switching the user equipment connected to the first IAB node to the second IAB node according to the second IAB node detected by the detecting means.

[0019] Advantageous Effects of the Invention

[0020] According to the present invention, a technology that can achieve more efficient communication can be provided. Other features and advantages of the present invention will become clear from the following description in conjunction with the accompanying drawings. Please note that throughout the drawings, the same reference numerals represent the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0022] Figure 1 is a block diagram showing the hardware arrangement of a communication device;

[0023] Figure 2is a block diagram showing the functional arrangement of a communication device;

[0024] Figure 3A is a diagram showing a system configuration before load distribution;

[0025] Figure 3B is a diagram showing a system configuration after load dispersion;

[0026] Figure 4 is a diagram showing a general switching sequence;

[0027] Figure 5 is a diagram showing a switching sequence in the first embodiment;

[0028] Fig. 6A This is a general operation flow chart for IAB donors regarding receiving notification information;

[0029] Figure 6B This is a general operation flow chart for IAB donors regarding receiving notifications of surrounding environment information;

[0030] Figure 7 is an operation flow chart of the IAB donor in the first embodiment;

[0031] Figure 8 is a diagram showing a switching sequence in the second embodiment;

[0032] Fig. 9 is an operation flow chart of the IAB donor in the second embodiment;

[0033] Fig.10 is an operation flow chart of the UE in the second embodiment; and

[0034] Fig.11 is a diagram showing a switching sequence in a modification. DETAILED DESCRIPTION

[0035] The embodiments will be described in detail below with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. A plurality of features are described in the embodiments, but the invention is not limited to requiring all of these features, but a plurality of such features may be appropriately combined. In addition, in the accompanying drawings, the same reference numerals are given to the same or similar configurations, and redundant descriptions thereof are omitted.

[0036] (First embodiment)

[0037] As a first embodiment of a communication device according to the present invention, the following is an example of a communication device operating as an IAB donor and a base station in a mobile communication system. The mobile communication system is, for example, a fifth generation (5G) mobile communication system. One or more IAB nodes are connected to the IAB donor, and the UE communicates with the IAB donor via the IAB node used as a relay node. The IAB node can be a RAN (Radio Access Network) node that supports both an NR (New Radio) access link and an NR backhaul link.

[0038] <Equipment Arrangement>

[0039] Figure 1 1 is a block diagram showing an example of the hardware arrangement of a communication device used as an IAB donor or an IAB node. The communication device 101 includes a control unit 102, a storage unit 103, a wireless communication unit 104, and an antenna control unit 105. The control unit 102 controls the entire device by executing a control program stored in the storage unit 103. The storage unit 103 stores the control program to be executed by the control unit 102 and various information to be used for control (cell information, connection terminal information, IAB routing information, etc.). When the control unit 102 executes the control program stored in the storage unit 103, various operations to be described later are implemented. The wireless communication unit 104 performs cellular network communications that comply with the 3GPP standard, such as LTE or 5G communications. The antenna control unit 105 controls the antenna used for the wireless communication performed by the wireless communication unit 104.

[0040] Figure 2 201 is a block diagram showing an example of the software function arrangement of a communication device used as an IAB donor or an IAB node. The communication device function 201 includes a signal transmission unit 202, a signal receiving unit 203, a data storage unit 204, a connection control unit 205, a notification information detection unit 206, a handover request unit 207, and a notification information generation unit 208. The signal transmission unit 202 and the signal receiving unit 203 perform cellular network communication conforming to the 3GPP standard with another device (such as a UE), such as LTE or 5G communication. The data storage unit 204 stores and saves software programs, IAB routing information, information about the connected terminal, etc.

[0041] The connection control unit 205 controls the wireless communication performed in the wireless communication unit 104. The detection unit 206 detects the notification information from the IAB node existing in the periphery. The handover request unit 207 issues a handover request by sending a radio resource control (RRC) message to the UE. The notification information generation unit 208 notifies a signal indicating the presence of the own device (communication device 101 as an IAB node).

[0042] <System Configuration and Schematic Operation>

[0043] Figure 3A and Figure 3B 1 and 2 are views each showing a system configuration, and particularly exemplarily show states before and after UE switching occurs and a load distribution process (to be described later).

[0044] IAB donor 311 includes IAB nodes 301 to 306 under control and is configured to establish a communication path indicated by path 320 between the donor and the plurality of nodes.

[0045] In a large event venue 330, many UEs 400 are gathered to form a UE group 331. The many UEs 400 included in the UE group 331 are basically connected to the IAB node 306 which is the nearest normal IAB node (a normal IAB node in the best radio wave condition). Therefore, the IAB node 306 is in an extremely high load state. In this case, Figure 3B As shown, in order to increase the communication capacity in the event venue 330 or to distribute the load, the IAB node 307 may be installed (eg, on a vehicle) as a backup IAB node.

[0046] In this state, it is necessary to quickly try to distribute the load from the high-load IAB node 306 to the backup IAB node 307. However, in the current 3GPP standard, handover is performed only when each UE is disconnected from the connected IAB node or when the IAB donor recognizes that handover is necessary based on the surrounding environment information collected from the UE.

[0047] In the latter case where the handover is caused by the IAB donor, more specifically, each UE collects surrounding environment information and notifies the surrounding environment information to the IAB donor 311, and the IAB donor 311 analyzes the notified surrounding environment information. Then, if the IAB donor 311 determines that it is better to hand over the UE to another IAB node, it notifies the UE of an RRC connection reestablishment request (RRC reconfiguration message). The format of the RRC reconfiguration message is defined in 3GPP TR 38.331 6.2.2. By performing this process, the handover of the UE to another IAB node is started.

[0048] As described above, in the current 3GPP standard, even if a standby IAB node is input, it is not possible to quickly switch the UE. That is, it is necessary to wait for the UE to be disconnected or the IAB donor to be determined. In addition, since the IAB donor receives the surrounding environment information notification from each UE via the IAB node, if the IAB node to be passed is in a high load state, the surrounding environment information notification from each UE is likely to be delayed.

[0049] In order to solve the above problem, in this embodiment, a form will be described, in which the IAB donor switches the UE from the high-load IAB node to the standby IAB node regardless of whether the surrounding environment information notification is received from the UE (without waiting for the reception completion). Specifically, the following will be described in which the UE 400 switches the UE from the high-load IAB node to the standby IAB node via the IAB node 306 ( Figure 3A ) When a communication path with the IAB donor 311 is established, a backup IAB node 307 is newly installed in the event venue 330 ( Figure 3B ) of the system.

[0050] First, we will refer to Figure 4 , Fig. 6A and Figure 6B The general operation of handover caused by IAB donor according to 3GPP standard is described. Then, reference will be made to Figure 5 and Figure 7 The operation of the handover caused by the IAB donor in the first embodiment is described.

[0051] <General handover operation according to 3GPP standards>

[0052] Figure 4 is a diagram showing a general switching sequence caused by an IAB donor. More specifically, Figure 4 The following shows a process in the case of switching the UE by determining the necessity of UE switching based on the surrounding environment information notified from the UE.

[0053] In S401, UE 400 sends its surrounding environment information to IAB node 306 to notify IAB donor 311 of the surrounding environment information. The surrounding environment information includes, for example, RSSI information of IAB nodes existing around UE. In S402, IAB node 306 sends (forwards) the received surrounding environment information to IAB donor 311.

[0054] In S403, based on the surrounding environment information notified from UE 400, IAB donor 311 sends a handover notification to IAB node 306 as needed to notify the notification source UE 400 of the handover notification. For this notification, the RCC reconfiguration message defined in the 3GPP standard is used. In S404, IAB node 306 sends (forwards) the received handover notification to UE 400.

[0055] In S405, the UE 400 that has received the handover notification performs a synchronization establishment process and a RACH process on the IAB node 307, and is connected to the IAB node 307. The synchronization establishment process and the RACH process are defined in the 3GPP standard and are performed when the UE is first connected to the IAB node. More specifically, they indicate a process of performing synchronization and RACH (random access channel) frequency determination processing between the UE and the IAB node, and a process of establishing link synchronization between the UE and the IAB node.

[0056] In S406, in order to notify the IAB donor 311 of the handover completion notification, the UE 400 sends a handover completion notification to the IAB node 306. For this notification, the RRC reconfiguration complete message defined in the 3GPP standard is used. In S407, the IAB node 306 sends (forwards) the received handover completion notification to the IAB donor 311.

[0057] Fig. 6A A general operation flow chart of an IAB donor regarding receiving notification information is shown. Figure 6B The general operation flow chart of the IAB donor on receiving the notification of surrounding environment information is shown. The order of these reception waiting processing operations is not limited, and the processing corresponding to the received content is performed sequentially. Generally, the IAB donor waits for detecting the notification information from the IAB node trying to connect to its own network and waits for receiving the surrounding environment information notified from the UE under the network (step F600).

[0058] In step F601, the IAB donor determines whether notification information from the IAB node is detected. If notification information is detected, the process proceeds to step F602. If notification information is not detected, the process returns to step F600.

[0059] In step F602, in order to make the IAB node that sent the detected notification information available in its own network, the IAB donor performs processing to incorporate the IAB node into its own network, such as path information reconstruction. Thereafter, the process returns to step F600. However, for example, if there is a reception waiting end instruction, the process ends.

[0060] In step F603, the IAB donor determines whether a surrounding environment information notification is received from the UE (via the IAB node). If a surrounding environment information notification is received, the process proceeds to step F604. If a surrounding environment information notification is not received, the process returns to step F600.

[0061] In step F604, the IAB donor checks the content of the ambient environment information notification and determines whether it is necessary to perform handover of the UE that sent the ambient environment information notification. If it is determined that handover is necessary, the process proceeds to step F605. If it is determined that handover is not necessary, the process returns to step F600.

[0062] In step F605 , the IAB donor sends a handover notification to the UE (via the IAB node).

[0063] <Switching Operation in First Embodiment>

[0064] Figure 5 FIG. 3 is a diagram showing a switching sequence caused by the IAB donor in the first embodiment. In the sequence, the IAB node 308 is defined as a high-load IAB node (corresponding to the IAB node 306 ), and the IAB node 309 is defined as a standby IAB node (corresponding to the IAB node 307 ).

[0065] UE 400 builds a communication path with IAB donor 311 via IAB node 308. In an attempt to distribute the load on IAB node 308, IAB node 309 is newly installed.

[0066] In S501, the IAB node 309 sends notification information to notify its own existence through a beacon, a dedicated message, etc. At this time, the notification information may include information indicating that "the own node is an IAB node installed as a spare", or information indicating that "the own node is an IAB node installed as a spare of the IAB node 308".

[0067] The notification information is sent according to the 3GPP standard (9.3.1 of 3GPP TS 38.413), in particular, according to the notification information format defined in the radio network layer. This format is a format that allows notification by including up to 256 types of information. The above notification information is added to a part of the reserved area or the free area in the current standard and sent.

[0068] In S502, the IAB donor 311 that has detected the notification information from the IAB node 309 performs an IAB node check process. In this check process, it is determined whether the detected IAB node can be used as a backup IAB node for the IAB node 308.

[0069] For example, by using the location information of each of the IAB node 308 and the IAB node 309, it is determined whether the IAB node 309 exists in a position that can be used as a backup IAB node according to the location relationship between the two IAB nodes. Alternatively, it can be determined whether the notification information includes information indicating that "the own node is an IAB node installed as a backup" or information indicating that "the own node is an IAB node installed as a backup of the IAB node 308".

[0070] In S503, the IAB donor 311 performs a process of deciding one or more UEs to be the handover execution targets. That is, this is a process for selecting one or more UEs to be handed over to the standby IAB node from the UEs connected to the high-load IAB node. If it is determined in the above-mentioned determination process that the UEs connected to the high-load IAB node can be connected to the standby IAB node to distribute the load, the decision process is performed.

[0071] For example, the determination is made based on "the number of UEs connected to the high-load IAB node (e.g., whether the number of UEs exceeds a threshold value determined separately)" or "weighted according to the bandwidth used by the switching target UE", and one or more UEs that can achieve effective load distribution are set as switching targets. For example, UEs exceeding the threshold are randomly selected and determined as switching targets. Alternatively, for example, based on the information on the bandwidth used by each UE (the proportion of the load on each UE in the high-load IAB node), one or more UEs can be selected in descending or ascending order of the bandwidth used.

[0072] In S504, the IAB donor 311 sends a handover notification to the IAB node 308 to notify the UE set as the handover target of the handover notification. For this notification, the RRC reconfiguration message defined in the 3GPP standard is used. More specifically, a dedicated SIB1 transmission message in a defined format is used to specify the ID of the IAB node 309 as the reconnection destination. Alternatively, a new definition dedicated to the notification can be added to the RRC reconfiguration message field. In S505, the IAB node 308 sends (forwards) the received handover notification to the UE 400.

[0073] The UE 400 that has received the handover notification performs handover to the designated IAB node 309. The subsequent processes (S506 to S508) are similar to the general handover operation (S405 to S407) according to the 3GPP standard.

[0074] Figure 7 The following is a flowchart showing the operation of the IAB donor in the first embodiment: The IAB donor waits for detection of receiving notification information from an IAB node attempting to connect to its own network.

[0075] In step F701, the IAB donor detects notification information from the IAB node. The following description assumes that the notification information is detected.

[0076] In step F702, the IAB donor performs a process of incorporating the IAB node that has transmitted the detected notification information into its own network (this process is similar to step F602).

[0077] In step F703, the IAB donor performs a load determination as to whether there is a high-load IAB node (among one or more IAB nodes under the control of the IAB donor) on the network. If it is determined that there is a high-load IAB node, the process proceeds to step F704. If it is determined that there is no high-load IAB node, the process ends.

[0078] For example, a threshold value for processing load or traffic congestion rate is used as a determination criterion, and an IAB node that is frequently in a high-load state or congestion occurs is detected as a high-load IAB node.

[0079] In step F704, the IAB donor determines whether the IAB node that sent the notification information detected in step F701 can be used as a backup IAB node for the high-load IAB node. If it is determined that the IAB node can be used as a backup IAB node, the process proceeds to step F705. If it is determined that the IAB node cannot be used as a backup IAB node, the process ends.

[0080] For example, by using the position information of the high-load IAB node and the position information of the detected IAB node, it is determined whether the detected IAB node exists in a position where it can be used as a backup IAB node according to the positional relationship between the two IAB nodes. Alternatively, it may be determined whether the notification information detected in step F701 includes information indicating that "the own node is an IAB node installed as a backup" or information indicating that "the own node is an IAB node installed as a backup of a specific high-load IAB node".

[0081] In step F705, the IAB donor performs a process of deciding a UE to be a handover target. That is, the IAB donor determines a UE to be a handover execution target among UEs connected to the high-load IAB node.

[0082] This determination process is performed to appropriately switch the UE connected to the high-load IAB node to the standby IAB node. For example, the determination is made based on "the number of UEs connected to the high-load IAB node (e.g., whether the number of UEs exceeds a threshold determined separately)" or "weighted based on the usage bandwidth of the switching target UE", and one or more UEs that can achieve effective load distribution are set as switching targets.

[0083] In step F706, the IAB donor sends a handover notification to one or more UEs decided in step F705. For this notification, the RRC reconfiguration message defined in the 3GPP standard is used. More specifically, a dedicated SIB1 transmission message in a defined format is used to specify the ID of the standby IAB node as the reconnection destination. Alternatively, a new definition dedicated to the notification can be added to the RRC reconfiguration message field.

[0084] The order of steps F701 to F706 is not limited to the above order. For example, the processing order of steps F703 and F704 can be changed. If the notification information detected in step F701 includes information indicating that "the own node is an IAB node installed as a backup for a specific high-load IAB node", it can be considered that the IAB node is installed intentionally. That is, it can be considered that the IAB node is installed as a backup IAB node, not limited to load distribution for high-load IAB nodes. In this case, even if a high-load IAB node cannot be detected on the network in step F703, switching notification to the UE (steps F705 and F706) can be performed.

[0085] As described above, according to the first embodiment, if a new IAB node is detected and a predetermined condition is satisfied, a handover caused by the IAB donor is performed. Here, the predetermined condition is that one or more existing IAB nodes include a high-load IAB node, and the new IAB node can be used as a backup for the high-load IAB node. That is, one or more UEs are switched from the high-load IAB node to the backup IAB node without waiting for detection of a disconnection of the UE or notification of surrounding environment information from the UE.

[0086] Through this control, if a new IAB node is installed in a state where many UEs are concentrated, it is possible to quickly switch UEs and effectively disperse the communication load.

[0087] (Second embodiment)

[0088] In the second embodiment, a form will be described in which, in addition to the operation in the first embodiment, the UE that receives the switching notification from the IAB donor further checks whether the switching is possible. This form assumes a case in which it is desired to limit the UEs that can be connected to the standby IAB node to the UEs used by the active participant. Note that the operation of the IAB donor and the IAB node, as well as the device arrangement and system configuration are similar to those in the first embodiment ( Figures 1 to 3B , Figure 5 and Figure 7 ) and its description will be omitted.

[0089] <Switching Operation in Second Embodiment>

[0090] Figure 8FIG. 3 is a diagram showing a switching sequence caused by an IAB donor in the second embodiment. In this sequence, as in the first embodiment, IAB node 308 is defined as a high-load IAB node (corresponding to IAB node 306), and IAB node 309 is defined as a standby IAB node (corresponding to IAB node 307).

[0091] UE 400 builds a communication path with IAB donor 311 via IAB node 308. In an attempt to distribute the load on IAB node 308, IAB node 309 is newly installed. The processing in S801 to S803 is similar to the processing (S501 to S503) in the first embodiment, and description thereof will be omitted.

[0092] In S804 , the IAB donor 311 sends a handover notification to the IAB node 308 to notify the UE 400 set as the handover target of the handover notification. In S805 , the IAB node 308 sends (forwards) the received handover notification to the UE 400 .

[0093] For this notification, the RRC reconfiguration message defined in the 3GPP standard is used. More specifically, a dedicated SIB1 transmission message in a defined format is used to specify the ID of the IAB node 309 as the reconnection destination. Alternatively, a new definition dedicated to this notification can be added to the RRC reconfiguration message field. For example, as the newly defined information, information indicating "switching to a standby node" is added. By giving this information, the UE that receives the switching notification can recognize that the switching is a switching to a standby IAB node.

[0094] In S806 , the UE 400 that has received the handover notification checks whether it can handover to the designated standby IAB node (here, the IAB node 309 ).

[0095] If it is determined in S806 that the handover is not feasible (NG in check), the UE 400 sends a handover not feasible notification to the IAB donor 311 via the IAB node 308 in S807 and S808. Several methods are available as a method of notifying the IAB donor of the message. For example, a method of notifying the message by including handover not feasible information in the RRC reconfiguration complete message is available. A method of newly setting an RRC message for the message is also available.

[0096] If it is determined in S806 that handover is possible (OK in check), UE 400 performs handover to designated IAB node 309. The processing in this case (S809 to S811) is similar to a general handover operation (S405 to S407) according to the 3GPP standard.

[0097] Fig. 9An operation flow chart of the IAB donor in the second embodiment is shown. Note that the processing except step F906 is similar to the processing (F701 to F705) in the first embodiment, and the description thereof will be omitted.

[0098] In step F906, the IAB donor sends a handover notification to one or more UEs decided in step F905. For this notification, the RRC reconfiguration message defined in the 3GPP standard is used. Here, a new definition indicating "handover to a standby node" is added to the RRC reconfiguration message field.

[0099] Note that the order of steps F901 to F906 is not limited to the above order. For example, the processing order of steps F903 and F904 may be changed.

[0100] Fig.10 The operation flow chart of the UE in the second embodiment is shown. The flow chart assumes that the UE receives a handover notification.

[0101] In step F1001 , the UE receives a switching notification from the IAB donor.

[0102] In step F1002, the UE determines whether the handover notification includes information indicating "handover to the backup node". If the information is included, the process proceeds to step F1003. If the information is not included, the process proceeds to step F1004. Note that if the IAB donor makes Figure 6B The general handover notification shown (according to the 3GPP standard) does not include information indicating "handover to the backup node" in the notification.

[0103] In step F1003, the UE regards the received handover notification as a notification of handover to the standby IAB node. Then, the UE determines whether it can handover to the designated standby IAB node. If it is determined that the handover is possible, the process proceeds to step F1004. If it is determined that the handover is not possible, the process proceeds to step F1005.

[0104] For example, a method of checking whether the UE has passed a specific authentication (such as MAC address authentication or 802.1X authentication) in advance can be used as a determination method. For example, the UE is set to pre-access an authentication site provided by an operator. If the authentication is successful, information indicating the successful authentication is stored in the system information. At this time, if the operator has prepared a spare IAB node, information that can identify the spare IAB node can also be stored. The UE refers to the system information when checking in S806 and decides whether it can be switched based on the current authentication status.

[0105] As another example, a method of checking whether the standby IAB node actually exists within the connection range of the handover target UE is available. That is, the conventional handover caused by the IAB donor is based on the surrounding environment information notification from the UE. That is, the IAB donor receives the surrounding environment information notification from the UE, and it can ensure that the standby IAB node exists within the connection range of the UE. However, this is not guaranteed in the second embodiment, so the check as described above is assumed.

[0106] As a specific checking method, for example, there is a method of checking whether the designated standby IAB node exists in the IAB node list generated by the UE scanning the surrounding environment. There is also a method of checking whether the designated standby IAB node exists by the UE scanning the surrounding environment when receiving a handover request.

[0107] In step F1004, the UE performs a normal handover process (according to the 3GPP standard). On the other hand, in step F1005, the UE sends a handover impracticable notification to the IAB donor. Several methods can be used as a method of notifying the IAB donor of the message. For example, a method of notifying the IAB donor of the message by including handover impracticable information in an RRC reconfiguration complete message, a method of newly setting an RRC message for the message, etc. are available.

[0108] As described above, according to the second embodiment, the US that receives the switching notification checks whether switching is possible. For example, in order to limit the UEs that can be connected to the standby IAB node to the UEs used by the active participant, it is determined whether switching is possible by checking whether the UE has passed a specific verification in advance. Even in the case where it cannot be guaranteed that the standby IAB node exists within the connection range of the UE, load distribution can be appropriately controlled.

[0109] (Revision)

[0110] In the first and second embodiments, it has been described that the IAB donor decides the handover target UE, but an existing (high-load) IAB node may be configured to decide the handover target UE.

[0111] <Switching Operation in Modified Example>

[0112] Fig.11 3 is a diagram showing a switching sequence caused by the IAB donor in the modification. In this sequence, as in the first embodiment, the IAB node 308 is defined as a high-load IAB node (corresponding to the IAB node 306), and the IAB node 309 is defined as a standby IAB node (corresponding to the IAB node 307).

[0113] UE 400 builds a communication path with IAB donor 311 via IAB node 308. In an attempt to distribute the load on IAB node 308, IAB node 309 is newly installed. The processing in S1101 to S1102 and S1106 to S1108 is similar to the processing (S501 to S502 and S506 to S508) in the first embodiment, and a description thereof will be omitted.

[0114] In S1103, the IAB donor 311 sends a handover notification to the IAB node 308 to notify the IAB node 308 of the UE handover start request. For this notification, the RRC reconfiguration message defined in the 3GPP standard is used. However, at this time, the handover start request is included, but the specific handover target UE is not specified. Therefore, a new definition for indicating the handover start request can be added to the message field.

[0115] In S1104, the IAB node 308 performs a process of deciding one or more UEs to be the handover targets. This decision process is similar to the process (S503 and S803) performed by the IAB donor in the first and second embodiments.

[0116] In S1105 , the IAB node 308 sends (forwards) the handover notification received in S1103 to the one or more UEs determined in S1104 .

[0117] Note that in S1104 , the IAB node 308 may make a determination based on whether the connected UE has passed a specific authentication. In this case, the IAB node 308 may be configured to obtain information indicating whether each UE has passed a specific authentication from the IAB donor 311 .

[0118] For example, the UE is set to pre-visit a verification site provided by the operator. If the verification is successful, information indicating the verification success is stored in the system information. The UE notifies the IAB donor of the information in the environmental information notification process with the IAB donor. At this time, if the operator has prepared a spare IAB node, information that can identify the spare IAB node can also be stored. For example, an area for the information can be newly set in the measurement report-IE field in the measurement report message to notify the IAB donor of the information.

[0119] Thus, the IAB donor can specify the UE of the active participant based on the surrounding environment information of the UE acquired before the congestion. Therefore, the handover notification to the UE that is not an active participant can be suppressed, thereby reducing the number of messages in the entire system.

[0120] (Other embodiments)

[0121] The present invention can be implemented by providing a program for implementing one or more functions of the above-mentioned embodiments to a system or device via a network or storage medium, and causing one or more processors in a computer of the system or device to read and execute the program. The present invention can also be implemented by a circuit (such as an ASIC) for implementing one or more functions.

[0122] The present invention is not limited to the above-described embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, in order to make the public aware of the scope of the present invention, the following claims are made.

[0123] This application claims the benefit of Japanese Patent Application No. 2022-083990, filed on May 23, 2022, which is hereby incorporated herein by reference.

Claims

1. A communication device, the communication device operating as an integrated access and backhaul IAB donor, the IAB donor being configured to communicate with a first IAB node in a mobile communication system, characterized in that: The communication device comprises: a detection device, the detection device being configured to detect a second IAB node different from the first IAB node; and A sending device is used for sending a handover request for handing over a user equipment connected to the first IAB node to the second IAB node according to the detection device detecting the second IAB node.

2. The communication device according to claim 1, characterized in that The communication device further comprises: a determining device, the determining device being used to determine whether the second IAB node can be used for load distribution of the first IAB node, If the determining means determines that the second IAB node can be used for load distribution of the first IAB node, the sending means sends the switching request.

3. The communication device according to claim 2, characterized in that The communication device further comprises: a load determination device, the load determination device being used to determine whether the first IAB node is in a load state higher than a predetermined threshold, The determining means determines whether the second IAB node can be used to distribute the load of the first IAB node determined by the load determining means to be in a higher load state.

4. The communication device according to any one of claims 1 to 3, characterized in that: The mobile communication system is a fifth generation 5G mobile communication system, and The first IAB node and the second IAB node support both a backhaul link and an access link.

5. The communication device according to any one of claims 1 to 4, characterized in that: The transmitting means transmits the handover request by using a radio resource control RRC message.

6. The communication device according to any one of claims 1 to 5, characterized in that: The sending means sends the handover request regardless of whether a surrounding environment information notification from a user equipment connected to the first IAB node is received.

7. The communication device according to any one of claims 1 to 6, characterized in that: The detecting means detects the second IAB node by receiving notification information indicating the existence of the second IAB node, and The notification information includes first information indicating that the second IAB node is an IAB node installed as a standby node of the first IAB node.

8. The communication device according to claim 7, characterized in that: If the first information is included in the notification information, the sending means includes information indicating switching to a standby node in the switching request.

9. The communication device according to claim 2, characterized in that: The determining means determines whether the second IAB node can be used for load distribution of the first IAB node based on the location information of the first IAB node and the location information of the second IAB node.

10. The communication device according to claim 2, characterized in that The detecting means detects the second IAB node by receiving notification information indicating the existence of the second IAB node, and The determination means determines whether the second IAB node can be used for load distribution of the first IAB node based on whether the notification information includes first information indicating that the second IAB node is an IAB node installed as a spare for the first IAB node.

11. The communication device according to any one of claims 1 to 10, characterized in that: The communication device further comprises: a decision device, the decision device being used to decide one or more user equipments to be the handover targets in the handover request, The sending device sends the switching request to the one or more user equipments determined by the determining device.

12. The communication device according to claim 11, characterized in that If the number of user equipments connected to the first IAB node exceeds a threshold, the decision means decides the user equipments whose number exceeds the threshold as one or more user equipments to be handover targets.

13. The communication device according to claim 11, characterized in that The decision means decides one or more user equipments to be a handover target based on information on the used bandwidth of each user equipment connected to the first IAB node.

14. The communication device according to claim 11, characterized in that The decision means decides one or more user equipments to be a handover target based on an authentication state of each user equipment connected to the first IAB node in a predetermined authentication site.

15. A mobile communication system, comprising a base station, a first relay node, and a user equipment configured to communicate with the base station via the first relay node, characterized in that: The base station comprises: a detection device, the detection device being configured to detect a second relay node different from the first relay node, and a sending device, the sending device being configured to send a handover request for handing over a user equipment connected to the first relay node to the second relay node according to the detection device detecting the second relay node, and The user equipment comprises: a receiving device, the receiving device being configured to receive the handover request from the base station, a second determining device, the second determining device being used to determine whether it is possible to switch to the second relay node indicated by the switching request, and Notification means, the notification means is used to send a notification to the base station if the second determination means determines that the handover to the second relay node cannot be performed.

16. A mobile communication system, comprising a base station, a first relay node, and a user equipment configured to communicate with the base station via the first relay node, characterized in that: The base station comprises: a detection device, the detection device being configured to detect a second relay node different from the first relay node, and a first sending device, the first sending device being configured to send, to a first relay node, a first switching request for switching a user equipment connected to the first relay node to the second relay node according to the detection device detecting the second relay node, and The first relay node comprises: a receiving device, the receiving device being configured to receive the first handover request from the base station, a decision device, the decision device being configured to decide one or more user equipments to be a handover target based on the first handover request, and The second sending means is used to send a second switching request indicating switching to the second relay node to the one or more user equipments determined by the determining means.

17. A control method for a communication device, the communication device operating as an IAB donor, the IAB donor being configured to communicate with a first IAB node in a mobile communication system, characterized in that: The control method comprises: a detecting step of detecting a second IAB node different from the first IAB node; and A sending step of sending a handover request for handing over the user equipment connected to the first IAB node to the second IAB node according to the second IAB node being detected in the detecting step.

18. A program for causing a computer including a communication unit to operate as the communication device according to any one of claims 1 to 14.

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